Malignant tachyarrhythmia, for example, ventricular fibrillation, is an uncoordinated contraction of the cardiac muscle of the ventricles in the heart, and is the most commonly identified arrhythmia in cardiac arrest patients. If this arrhythmia continues for more than a few seconds, it may result in cardiogenic shock and cessation of effective blood circulation. As a consequence, sudden cardiac death (SCD) may result in a matter of minutes.
In patients at high risk of ventricular fibrillation, the use of an implantable cardioverter defibrillator (ICD) system has been shown to be beneficial at preventing SCD. An ICD system includes an ICD, which is a small battery powered electrical shock device, may include an electrical housing, or can electrode, that is coupled to one or more electrical lead wires placed within the heart. If an arrhythmia is sensed, the ICD may send a pulse via the electrical lead wires to shock the heart and restore its normal rhythm.
Subcutaneous implantable cardioverter-defibrillator (SubQ ICD) systems have been devised to deliver electrical impulses to the heart by the use of a defibrillation lead placed subcutaneously on the torso. However, the SubQ ICD is large and requires an output of around 80J of energy to be effective. The large size of the SubQ ICD compromises patient comfort and has been known to erode through the skin after implantation. In addition, the SubQ ICD system is incapable of delivering anti-tachycardia pacing (ATP), which is a standard therapy in transvenous ICDs to painlessly terminate lethal tachyarrhythmias.
Owing to the large size and cost of the SubQ ICD device, and its inability to deliver painless therapy, it is desirable to provide method of implantation of a medical lead that is minimally traumatic, and also provides a pathway for a medical lead that does not require such a large output of energy for defibrillation. While tunneling tools have been devised to create a subcutaneous pathway for implantation of medical leads, current tunneling tools have fixed configurations and thus provide limited maneuverability through the tough tissues within the torso. Moreover, the pathway from the center of the chest to a position proximate the heart includes sensitive and easily punctured tissues, such as the heart and the lungs. Thus, it is desirable to provide a flexible tunneling tool that facilitates the creation of a pathway for insertion of medical lead without damaging sensitive tissue.